The present invention generally relates to decontamination methods and apparatus, and more particularly to methods and apparatus for removing contaminated exterior and interior surfaces of large bore pipes and exterior surfaces of structural steel elements.
Proper decontamination or disposal of contaminated structures is an ongoing problem. Pipes used in radiological environments, for example, are often exposed to radioactive material, such as uranium, which contaminates the pipe. Consequently, when the contaminated pipe is no longer in use, it must be handled as radioactive waste. Only certain types of sites or disposal cells are suitable for receiving radioactive waste. The disposal cells are expensive to build, and have a limited holding capacity. The limited capacity has created a backlog of radioactively contaminated waste, including pipe, which requires disposal. As more radiologically contaminated sites are deactivated and decommissioned, the backlog is expected to grow significantly.
Unfortunately, structures such as pipes are not efficiently disposed of in disposal cells. If disposed directly in the cell, the pipes create voids in the cell which waste available space and create potentially unstable loading in the cell. To minimize the voids, the pipe may be cut in half or filled with a grout material. Either of these approaches, however, is labor intensive and overly costly to perform, especially when processing large volumes of pipe.
One alternative to direct disposal is to recondition the structures for reuse or disposal as low level radioactive material. This approach has the potential benefit of effectively recycling the structure if it is suitable for reuse, thereby conserving resources. Many regulations applicable to radioactive pipe reconditioning exist which require set quality standards for reconditioned structures. Typically, the reconditioned structures must have a near-white metal finish. As a result, many current surface removing methods and apparatus are not suitable for radioactive pipe reconditioning. It is also important for reconditioning equipment to be portable, so that reconditioning may be performed on site. This requirement eliminates additional known surface removing methods which are not easily transported.
Furthermore, the methods which are portable and provide the necessary finish are often overly cumbersome and difficult to use. When the contaminated structure is a pipe, both an inner surface and an outer surface are often be contaminated. Currently, hand held decontamination tools, such as ROTO PEEN(trademark) scalers, are used to decontaminate outer pipe surfaces. Inner pipe surface decontamination typically requires the use of chemicals to remove the contaminated portions. Conventional pipe reconditioning, therefore, is overly difficult and involves the use, handling, and cleanup of chemicals.
After removing the surfaces of a structure such as a pipe, it must be analyzed to determine the level, if any, of remaining contamination and appropriately characterized. As with surface removal, the geometry of the reconditioned structure may also increase the difficulty of structure characterization. One currently known method of analyzing pipe requires sample readings, or xe2x80x9cswipesxe2x80x9d, to be taken from various surface portions of the structure. The swipes are typically taken in the field and interpreted by a field instrument or taken to a laboratory where the swipes are read by bench top equipment such as liquid scintillation counters. This method is overly costly, and requires a significant amount of turn around time.
In accordance with certain aspects of the present invention, apparatus is provided for decontaminating a structure having exterior and interior surfaces. The apparatus comprises a housing having an inlet and an outlet and a conveyor extending from the housing inlet to the housing outlet. An exterior surface removing station is disposed inside the housing near a first portion of the conveyor and includes a grit blaster adapted to project an abradant toward the exterior surface of the structure. An interior surface removing station is disposed inside the housing near a second portion of the conveyor and includes a movable blast lance adapted to project an abradant toward the interior surface of the structure. A collection assembly is positioned at a bottom of the housing for collecting spent abradant and removed surface fragments.
In accordance with additional aspects of the present invention, a decontamination and characterization system is provided for decontaminating and characterizing a radioactively contaminated structure having interior and exterior surfaces. The system comprises a decontamination module having a housing with an inlet and an outlet, and a conveyor extending from the housing inlet to the housing outlet. An exterior surface removing station is disposed inside the housing near a first portion of the conveyor, the exterior surface removing station including a grit blaster adapted to project an abradant toward the exterior surface of the structure. An interior surface removing station is disposed inside the housing near a second portion of the conveyor, the interior surface removing station including a movable blast lance adapted to project an abradant toward the interior surface of the structure. A collection assembly is associated with the housing for collecting spent abradant and removed surface fragments. A characterization module is positioned downstream of the decontamination module and has a housing with an inlet and an outlet, and a conveyor extending from the housing inlet to the housing outlet. A material analyzer is positioned inside the housing, the material analyzer detecting radioactive contamination in both the interior and exterior surfaces of the structure and generating contamination data. A computer is electrically connected to the material analyzer for interpreting the contamination data and generating characterization information.
In accordance with further aspects of the present invention, an integrated decontamination and characterization system is provided for decontaminating and characterizing a pipe having an interior surface and an exterior surface. The system comprises a decontamination module having a housing with an inlet and an outlet, and a conveyor extending from the housing inlet to the housing outlet. An exterior surface removing station is disposed inside the housing near a first portion of the conveyor, the exterior surface removing station including a grit blaster adapted to project an abradant toward the exterior surface of the structure. An interior surface removing station is disposed inside the housing near a second portion of the conveyor, the interior surface removing station including a movable blast lance adapted to project an abradant toward the interior surface of the structure, and a collection assembly for collecting spent abradant and removed surface fragments. A characterization module is positioned downstream of the decontamination module and has a housing with an inlet and an outlet, and a conveyor extending from the housing inlet to the housing outlet. A material analyzer is positioned inside the housing, the material analyzer detecting radioactive contamination in both the interior and exterior surfaces of the structure and generating contamination data. A computer is electrically connected to the material analyzer for interpreting the contamination data and generating characterization information. An off-loading module is positioned downstream of the characterization module and has a sorter adapted to receive the characterization information and direct the pipe to a collection point associated with the characterization information. A ventilation module has a housing, a fan disposed in the housing and having an inlet in fluid communication with an interior of the decontamination module housing and an outlet exhausting to atmosphere, and an airborne particulate remover positioned inside the housing and in fluid communication upstream of the fan inlet.
In accordance with still further aspects of the present invention, apparatus is provided for removing an interior surface of a pipe. The apparatus comprises an elevator mechanism positioned to engage and lift an end of the pipe so that the pipe is oriented at an incline angle. A motorized wheel is associated with the elevator mechanism and is adapted to engage an exterior surface of the pipe, the motorized wheel rotating to spin the pipe. A blast lance is supported substantially at the incline angle and movable into the pipe to direct an abradant at the interior surface.
Other features and advantages are inherent in the apparatus claimed and disclosed or will become apparent to those skilled in the art from the following detailed description and its accompanying drawings.